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IO28                            Appendix VL

blank by the tool point.   A rack traverse v is provided for setting,                      *'

and a nut clamp at a for the leading screw.

The lower diagram of Fig. 934^ is a cross-section through the
saddle w, shewing the shaft p and bevels T rotating the cam u,
the shape of which is seen above. The spring d within the saddle                      j

causes slide x to bear upon the cam through the stop z, and as                      !

the milling cutter slowly revolves with the mandrel, the tool in                      j

rest b commences to cut on the circumference of the blank, sinks                      j

deeper, and emerges suddenly for a second tooth, as previously
described. The traverse can be at times prevented while all the
other motions are retained, by releasing the half-nuts at E, a
method required when forming spur-wheel and such-like cutters as                     ^

at Fig. 186, p. 178.     In fact, that diagram and the attached de-                      !

scription shew clearly the advantage of machine-relieved milling
cutters, where the relief angle is. the same for any radius ; and it                      \

follows that if only the front of the tooth be ground by a suitable
emery wheel, held with its flat surface as a radius of the cutter,                      \

the form of tooth is invariable so long as the cutter lasts.    The                      j

object  of Reinecker's  lathe is to make  this  condition for all                      t

milling cutters and not merely for those in Fig. 186.                                            ;,

Various cutters in process of turning and relieving are given in                       f

Fig. 934^.     That at A is a spur-wheel cutter where no traverse is                       ]

required.     The direction of rotation and cam reciprocation is                       |

shewn in every case by arrows.    Thus at B the top slide is turned                       I

round through 90, and its reciprocations are in a longitudinal                    Ufa

direction, which are the motions required for the special face-                f

cutter shown; and again the traverse is put out of action. Other
face-cutters are being tooled at D and E, while the special mills at
c and F require no further explanation,

Referring again to Fig. 934*2, the upper diagrams illustrate the
copying attachment required for the cutting of solids of revolution
other than simple cylinders. A long bracket/is fixed firmly to
the back of the bed, and carries a rigid, copy h, representing the
profile of the required cutter. The saddle w carries the recipro-
cating slide x as usual for the formation of the cutter teeth by
relief motion ; but the tool box is placed on a second slide e on
the top of x, which is pressed forward by a spring so as to cause                      ^

the pointer/to rest on the copy ^z, thus transferring the profile to                       J